From European Patent No. EP 0 501 612, a fuel injection system is already known in which a fuel-supply line is directly integrated in a valve seat. The valve seat, into which a fuel injector is insertable, is part of an intake manifold. The fuel system includes multiple-part manifolds which have flanges at their ends by which they are interconnected. The intake manifolds are either made of aluminum or plastic, and each of the valve seats usually surrounds a fuel injector with a radial clearance since, for instance, the fuel is supplied in the valve seats to fuel injectors embodied as so-called side-feed injectors. The fuel injectors are inserted into these valve seats in their fully assembled state. The fuel injector must be sealed in the valve seat by at least two sealing rings.
Furthermore, a fuel injection system is known from U.S. Pat. No. 5,568,798 in which a fuel-supply line is likewise integrated at an intake manifold. The fuel-supply line is in direct contact with a fuel injector to which the line supplies fuel. The fuel injector extends along a receiving orifice in the wall of the intake manifold and projects into it by its downstream end. The fuel-supply line includes an electrical line system, so that an electrical contacting of the valves takes place when the fuel injectors are inserted in the receiving bore.
Furthermore, from German Patent Application No. DE 196 00 378, a fuel-injection system is already known which is distinguished by an especially high integration of various components of the fuel injection. In this case, the fuel injection system includes at least one fuel injector and at least one intake manifold as well as a fuel-supply channel, all of which are provided with a plastic extrusion coat. The full integration of the fuel injectors at an intake-manifold system formed from plastic has the result that both electrical and hydraulic interfaces are reduced or avoided. Thus, this leaves only one compact component which is very easy to mount on a cylinder head of an internal combustion engine. Means for the electrical contacting of the fuel injectors, such as connecting plugs, are also fully integrated in the plastic extrusion coat. This complex component has the disadvantage, however, of being difficult to manufacture and handle in the plastic-extrusion process.